The instant invention relates to plotting devices and more particularly to a plotting device which can be effectively utilized as a navigational instrument for plotting courses and also for determining relative angles between remote objects.
While a variety of different types of course plotting devices have been heretofore available for use as navigational instruments on boats, it has been found that most of the known course plotting devices are relatively difficult and awkward to operate. For this reason, it has been found that often many of the known course plotting devices cannot be reliably used to accurately plot course headings and that it is often impossible to use many of the known devices under rough sea conditions. In addition, most of the heretofore known plotting devices have not been easily operable to compensate for water currents, and therefore it has often been necessary to carry out independent vector calculations when using the known devices. Accordingly, for these reasons, the heretofore known plotting devices have not been entirely effective for plotting courses, and they have been highly prone to operator error, particularly when they have been used under rough sea conditions. Further, while it has long been recognized that it can be beneficial for boatsmen to be able to measure the relative angles or bearings between various remote objects in order to determine the positions of boats or to determine whether or not boats are on collision courses with other boats, none of the heretofore known plotting devices have been operative for taking relative bearing measurements of this type.
Devices representing the closest prior art to the invention of which the applicant is aware are disclosed in the U.S. patents to TAYLOR, U.S. Pat. Nos. 45,535, MILLER et al, 474,846, HAGAN, 726,677, DAVISON et al, 1,161,625, KENNEDY, 1,828,807, SIEFKER, 2,244,125, VAN SCIEVER, 2,433,249, and BANNER, 3,863,347. Of these references, the U.S. patents to TAYLOR and DAVISON et al are believed to be the most pertinent, but since they fail to suggest a device having the structural features of the plotting device of the instant invention or one which is operative in the simple and accurate manner of the device of the instant invention for plotting courses and/or for taking relative bearings, even these references are believed to be of only general interest.
The instant invention provides an effective plotting device which can be easily and accurately utilized for plotting courses, even under rough sea conditions, and which can also be utilized for measuring relative angles between remote objects. Specifically, the plotting device of the instant invention comprises first, second, third and fourth legs which are pivotally connected so that the first and second legs and the third and fourth legs are substantially parallel to each other and so that they cooperate to define a collapsible parallelogram structure, and means mounted at the point of pivotal connection between one pair of adjacent legs for determining the relative angle therebetween. The means for determining the angle between the pair of adjacent legs preferably comprises a true compass rose element which is mounted in the plotting device so that it remains substantially stationary with respect to one of the pair of adjacent connected legs when the first and second legs are pivoted relative to the third and fourth legs. The device preferably further comprises a magnetic compass rose element which is overlayed on the true compass rose element and mounted in concentric relation therewith so that it is rotatable relative to the true compass rose element, but so that it remains substantially stationary with respsect thereto when the first and second legs are pivoted relative to the third and fourth legs. The preferred embodiment of the device of the instant invention further comprises a vector element which is pivotally attached to one of the legs, and vector element angle determining means mounted at the point of pivotal attachment of the vector element for determining the relative angle between the vector element and the leg to which it is attached. The vector element is preferably adjustable to adjust the point along the extent thereof where it is pivotally attached and the vector element and the vector element angle determining means are preferably mounted so that they are adjustably positionable at a plurality of spaced points along the longitudinal extent of the leg to which they are attached and so that they remain substantially stationary with respect thereto when the first and second legs are pivoted relative to the third and fourth legs. In the preferred embodiment, the vector element and the leg angle determining means are either mounted at the point where the third leg of the device is pivotally connected to the first leg or where it is connected to the second leg, and the third leg is pivotally connected to the first and second legs so that it is adjustably positionable in substantially parallel relation to the fourth leg at a plurality of spaced points along the extents of the first and second legs, and the vector element angle determining means preferably comprises the leg angle determining means.
The second embodiment of the device of the instant invention which is operative for determining the relative angles between pairs of remote objects comprises the first, second, third and fourth legs, and the leg angle determining means, and first and second mirror elements. The first mirror element is mounted on the device where one of the third or fourth legs is attached to one of the first or second legs, and the second mirror element is mounted on the device where the same one of the third or fourth legs is attached to the other of the first or second legs. The first mirror element is mounted so that it remains stationary with respect to the adjacent one of the third or fourth legs when the first and second legs are pivoted relative to the third and fourth legs and the second mirror element is mounted on the device so that it remains stationary with respect to the adjacent one of the first or second legs when the first and second legs are pivoted relative to the third and fourth legs. Further, the first and second mirror elements are positioned so that they face generally toward one another when the third and fourth legs are in a predetermined position (preferably in perpendicular relation) relative to the first and second legs and the mirror elements are constructed so that an image of the second mirror element can be viewed in the first mirror element from the opposite side of the second mirror element from the first mirror element.
Accordingly, it is a primary object of the instant invention to provide a course plotting device which is simple to operate and which can be reliably used to accurately plot a course heading.
Another object of the instant invention is to provide a course plotting device which can effectively compensate for currents.
An even further object of the instant invention is to provide a plotting device which can be utilized for determining the relative bearings between pairs of remote objects.